Optical measuring instrument, such as inclinometers, range finders, height finders, and the like



1,833,553 METERS, AND THE LIKE NOV. 24, 1931. B ET AL OPTICAL MEASURING INSTRUMENT, SUCH AS INCLINO RANGE FINDERS, HEIGHT FINDERS,

Filed Jan.

, //v vav 70R AM 6% ATTOR/VEXS Patented Nov. 24, 1931 UNITED STATES, PATENT OFFICE AROHIBALD' BARR" AN JOHN MARTIN STRANG, or ANNIESLAND, GLASGOW, soo'rmmn, nssrenons T0 BARR AND sraoun, LIMITED, or GLASGOW, SCOTLAND OPTICAL MEASURING INSTRUMENT, soon AS INGLINOMETERS, RANGE rmnnns, HHEIGH'I nmnnns, AND THE LIKE Application filed January 11, 1930, Serial No. 420,205, and i n Great Britain January 23, 1929.

This invention relates to improvements in or connected with optical measuring instruments, such as inclinometers, constant base single observer rangefinders, heightfinders, and the like, of the type in which the meas urement ot angle is madeby displacement of the image or images of the object as seen in the eyepiece ot the instrument which is produced by movement longitudinally only of a retracting prism, or prisms, of small angle, to and fro along the pathot one, or both, of the convergent beams of light. In such instrumentsthe retracting prism (or each of the prisms) is maintained with its-maximum deviation in the plane of triangulation, its position angularly is not altered, and consequently the term of the scale is a scale of angles, which, say tor ranges, is a reciprocal scale, having the spacing crowded together at the-high ranges compared with the spacing at the low ranges. In the description and claims such instruments'will bereterred to generally as optical measuring instruments of the type defined.

The object of this invention is to make provisionwhereby the form otthe scale of measurement of such instrument is modified from that given. bylongitudinal movement only ot the retracting prism or prisms, tor example, to give indications of range on a unitorm scale, or on a uniform scale of log arithm 0t range, or on a unitorm scale of other function of range or of parallax.

According to this invention, an optical measuring instrument of the type" defined comprises, in combination witlr'a longitudinally movable retracting prism and means for moving the prism longitudinally, an an gularly inovablejretracting member in the optical system of the instrument, and means operated by the prism-moving means tor causing relative ang'ular movement between the prismand the-retractingmemberas the prism is moved longitudinally, the relative angular movement having a predetermined relationship to thelongitudinal movement, whereby the displacement ot-the image or images is determined. i

In the following description the applicaion of the invention to a rangefinder of the type referred to will be described.

- In one example according to this invention, two equal retracting prisms are mounted in close proximity and are movable longitudinally to and tro along the axis of one ot the beams of light and are movable angularly in opposite directions about the axis of the beam. In this arrangement as'the two prisms are moved longitudinally, they are simultaneously moved angularly in opposite directions.

The angular movement of the prisms may be arranged to be symmetrical from the position where the maximum deviation of both prisms is in-the plane ot the triangulation,

and such that as the prisms move angularly from that position, the component of their combined deviation in the plane of triangulation decreases while the components of their deviations in the plane at right angles neutralize each other.

It the two prisms were of equal refraction an error in halving would be introduced by their movement angularly it they were moved through equal and opposite angles. This error is due to the linear displacement of the beam in passing through the prisms. To eliminate this efiect, unequal amounts of angular movement may be imparted to the prisms, as they move longitudinally along the beam. Alternatively the two prisms may be made unequal in deviation by the amount necessary to maintain halving correct with equal movement angularly in opposite directions. I r

In'another example two single retracting prismsare used, onein each of the beams of light, these prisms being movable longitudinally and simultaneously movable angularly. In this case prisms of equal retraction may be used and their movements longitudinally and angularly may be equal asthe angular movement ot the prisms may be arranged. to cause each of the two images in the rangefinder to move in the halving direction by the same amount and in the same direction. The apparent effect in the rangefinder would then be a slight alteration in elevation while halving would remain correct. t

In a further example a retracting prism Jis providedin one of the convergent beams of the rangefinder movable longitudinally only, and a retracting prism, say a prism of zero retracting angle, that is a parallel plate of glass, is provided in one of theconvergent beams which is movable angularly only about an axis perpendicular to the "plane of triangulation and simultaneously with the longitudinally moving prisml V Some examples of means according to this invention vwill now be described w th reference to the accompanying drawings, in wh1chz- Figure l is a sectional. elevation and Figure 2 is a sectional plan illustrating a range fi-nderand one example of means. 7 r

Figure 3 is a sectional plan", Figure 4 is a sectional elevation of a part oi Figure-3 and Figure 5 is a sectional end view of Figure 4 illustrating a portion of a rangefiinder';

and a thirdexample' of means,

The example illustrated at Figures: 1'

and 2 comprises two retracting prisms A A which are movable longitudinally to and froialong the path of one 'o'lf the convergent beams,- a'ndare movable angularly about the axis of the beam,1in. opposite directions'n These movements areproduced by rotational: motion applied to a working head 13' which is transmitted to pinionand'rack and pin andcam mechanisms. In the example illustrated there is a pinion 2 rotatable with the head 13, a rack 3 meshing with the pinion 2, a carrier 4: movable longitudinally with the rack13, two'frames, one for prism A the other for prism Aflwhich with the prisms are movable angularly in the carrier 4, theframeof prism A has-a radial pin 5 and-the frame of prism A has a radial pin 6, these pins engage respectively with cam slots 5 .and 6 :formed inplates which are fixed within a tube C- by which the objectives and eyepiece prism combination of the rangefinderare carried. Thus, ascarrier 4 and with it prisms A A aremoved longitudinally with rack 3, the engagement. of'pinst' and 6 with" thecam slots 5} and .6 respectively, causes the prisms A A 'to be also moved angularly in opposite directions.

'th'eeXample illustrated at Figures 8,

' i and 5,"'there is'one retracting 'pris'm"A in 5 one; of" the beams, movable longitudinally only,"an'd intheoth'e'r convergent beam there ,is a parallel'plateiof glass A? which is mo'v, able angularlyonly about a transverse axis" which is perpendicular tothe plane of triangulationj As in the former examples" 'prismiAf is movable endwise'by pinionf2 nieshing'withrack 3 on which prism A is" mounted; "The-plate of glass A is mounted in a-frame whiehis movable angu'larl-y about aprvot 7- and isiprovided with an arm hav a pin 8 which engages'in a cam slot 9 formed in a plate which is movable longitudinally with the raclr'3. r

We claim:

1. Anoptical measuring instrument of the 1.

type defined comprising,- in combination with a longitudinally movable retracting prism and means for moving the prism longitudinally,an angularlymovablerefractin'g member in the optica l 'systemof the instrument, and means operated by the prism-moving meansfor causing relative angular movement.

between the prism andthe retracting member as the prism is'mov ed longitudinally, the relative angularmovement having a predetermined relationship to the longitudinal movement. j 7 v p 2, optical measuring instrument of the type definedcomprising, in combination with iracting member in the optical system oftheg1 instrument movable longitudinallyand angularly, means for moving the prism longitudinally and simultaneously moving the refracting member longitudinally, and means operated by the prism-moving means for causing angular movement of the prism and of the retracting member simultaneously in opposite directions during their longitudinal movement, the angular- 'movements having a Vpre-determ'ined relationship to the longitudinalmovement. I V .e v 4. An optical measuring ..instrument of the type defined, comprising a longitudinally and angularly movable reiracting' prism, a

retracting member'in the optical system of r? the I instrument; movable longitudinally and angularly, means 'fonmoving the prism longitudinall y and simultaneously moving the Bil retracting inember longitudinally, and

means joperated by the prism-moving means 'ior causing angular movement of the prism of the retracting member simnltan'eously in oppositedirections about an axis parallel with the base" of itriangulation during their long tudinal movement, the angular movements having a predetermined relationship tojthelong'itudinal movement. n

An'optic'al measuring'instrument of the type defined comprisinga longitudinally and 'angularly movable retracting prism in one of the convergent beams of light, a retracting member in the same beam of light and movable longitudinally and angularly, means tor moving the prism longitudinally and simultaneously moving the retracting member longitudinally, and means operated by theprism-moving means for causing an gular movement of the prism and ot the reretracting member simultaneously in opposite directions during their longtiudinal movement, the angular movements having a predetermined relationship to the longitudinal movement.

6. a An optical measuring instrument of the type defined comprising a longitudinally and angularly movable retracting prism in one ot the convergent beams ot light, a retracting member in the other of the convergent beams ot light and movable longitudinally and angularly, means tor moving the prism longitudinally and simultaneously moving the retracting member longitudinally, and means operated by the prism moving means tor causing angular movement of the prism and ot the retracting member simultaneously during their longitudinal movement, the angular movements having a pre-determined relationship to the longitudinal movement.

7. An optical measuring instrument of the type defined comprising, in combination with a longitudinally movable retracting prism and means tor moving said prism, a retracting member in the optical system ot the instrument angularly movable about an axis perpendicular to the plane of triangulation but longitudinally fixed, and means operated by the prism-moving means tor causing angular movement of the retracting member as the prism is moved longitudinally, the relative angular movement having a pre-determined relationship to the movement longitudinally.

ARCHIBALD BARR. JOHN MARTIN STRANG. 

